1. Field of the Invention
The present invention relates to vehicle suspensions using pneumatic supports for the intermediate spring shackle mounting member of tandem axle springs.
2. Description of the Prior Art
In the prior art, various air or pneumatic spring suspension units have been advanced. For example, U.S. Pat. No. 2,771,303 issued to Frazier shows a tandem axle arrangement wherein the trailing end of the front suspension spring for the front axle and the leading edge of the suspension springs for the rear axle are connected to housings, each of which is supported directly by an air bag. However, each end of the axles is mounted in a separate bag, requiring smaller sized bags, resulting in higher pressures to withstand high loads used with semi-trailers. However, the individual assembly shows separate inflation for each side of the unit, causing the possibility of problems of uneven support pressures, and also making the device more likely to cause problems.
U.S. Pat. No. 4,099,740 issued to McGee also shows a pneumatic axle support system for tandem axles, which couples the springs used together and places the air bag directly over a coupling member between the rear end of the front spring and the front end of rear spring of a tandem assembly. Here, too, the air bags are at the side edges of the trailer, to support the two ends of the axles independently, providing for problems in control and operation.
Other patents which illustrate the state of the art and utilize air filled bags or cylinders for support of various axles include U.S. Pat. Nos. 2,790,650; 3,014,735; 3,224,522; 3,233,915; 3,309,107; and 3,762,487. These patents are of general interest and show various ways of supporting axles on inflatable members.